Add a script that finds dependencies for other OSs

This is used to make sure we also freeze versions for
packages that will only be used on Windows or OS X, while
the freezing script is most likely only be run on Linux.

contrib/deterministic-build/find_restricted_dependencies.py

@@ -0,0 +1,38 @@
+#!/usr/bin/env python3
+import sys
+
+import requests
+
+
+def check_restriction(p, r):
+    # See: https://www.python.org/dev/peps/pep-0496/
+    # Hopefully we don't need to parse the whole microlanguage
+    if "extra" in r and "[" not in p:
+        return False
+    for marker in ["os_name", "platform_release", "sys_platform", "platform_system"]:
+        if marker in r:
+            return True
+
+
+for p in sys.stdin.read().split():
+    p = p.strip()
+    if not p:
+        continue
+    assert "==" in p, "This script expects a list of packages with pinned version, e.g. package==1.2.3, not {}".format(p)
+    p, v = p.rsplit("==", 1)
+    try:
+        data = requests.get("https://pypi.org/pypi/{}/{}/json".format(p, v)).json()["info"]
+    except ValueError:
+        raise BaseException("Package could not be found: {}=={}".format(p, v))
+    try:
+        for r in data["requires_dist"]:
+            if ";" not in r:
+                continue
+            d, restricted = r.split(";", 1)
+            if check_restriction(d, restricted):
+                print(d, sep=" ")
+                print("Installing {} from {} although it is only needed for {}".format(d, p, restricted), file=sys.stderr)
+    except TypeError:
+        # Has no dependencies at all
+        continue
+

contrib/deterministic-build/requirements.txt

@@ -55,3 +55,6 @@ six==1.11.0 \
 urllib3==1.22 \
     --hash=sha256:06330f386d6e4b195fbfc736b297f58c5a892e4440e54d294d7004e3a9bbea1b \
     --hash=sha256:cc44da8e1145637334317feebd728bd869a35285b93cbb4cca2577da7e62db4f
+colorama==0.3.9 \
+    --hash=sha256:463f8483208e921368c9f306094eb6f725c6ca42b0f97e313cb5d5512459feda \
+    --hash=sha256:48eb22f4f8461b1df5734a074b57042430fb06e1d61bd1e11b078c0fe6d7a1f1

contrib/freeze_packages.sh

@@ -21,9 +21,14 @@ for i in '' '-hw' '-binaries'; do
     echo "OK."
 
     requirements=$(pip freeze)
+    restricted=$(echo $requirements | $other_python ./deterministic-build/find_restricted_dependencies.py)
+    requirements="$requirements $restricted"
+
     echo "Generating package hashes..."
+    rm $contrib/deterministic-build/requirements${i}.txt
+    touch $contrib/deterministic-build/requirements${i}.txt
 
-    echo "$requirements" | while IFS= read -r requirement ; do
+    for requirement in $requirements; do
         echo -e "\r  Hashing $requirement..."
         $other_python -m hashin -r $contrib/deterministic-build/requirements${i}.txt ${requirement}
     done